Tukai et al. 2002 - Sydney macroalgae arsenic speciation

Tukai and colleagues measured total arsenic and arsenic chemical forms in common marine macroalgae from the east coast of Australia. The samples were collected from rocky intertidal platforms near Sydney, not from retail seaweed products, so this page treats the results as raw macroalgae occurrence and speciation context for seaweed/kelp foods rather than a market-basket survey. Total arsenic, inorganic arsenic species, DMA, and arsenoriboside fractions are kept separate below.

Key numbers

The abstract reports total arsenic concentration ranges and class means in µg g-1:

Table 3 reports total arsenic and arsenic compounds in macroalgal extracts. Total As and extracted As are in µg g-1; species columns are percentages based on total arsenic concentration. Blank cells mean no value is reported in the extracted table; no zero or nondetect value was inferred.

Source-reported speciation summaries:

• Methanol/water extraction recovered 76-101% of arsenic from brown macroalgal species, 70-108% from green macroalgal species, and 83-95% from red macroalgal species.
• Characterizable arsenic compounds represented 46-95%, 38-85%, and 46-76% of extracted arsenic in brown, green, and red macroalgae, respectively.
• All macroalgal species contained arsenoribosides (9-99%).
• Glycerol-arsenoriboside and phosphate-arsenoriboside were found in all macroalgal species.
• Sulfonate-arsenoriboside and sulfate-arsenoriboside were found in brown macroalgal species and one red macroalgal species.
• Six macroalgal species contained high inorganic arsenic fractions (14.2-62.9%), and four species contained high DMA fractions (13.3-41.1%).
• The authors state that brown macroalgae generally contained more arsenic than green or red macroalgae, with species-level variation following brown > green > red overall.

Quality-control rows in Table 3 and the Methods section:

Methods (brief)

The study collected 13 macroalgal species near Sydney, New South Wales, Australia: Cape Banks and Bare Island at Botany Bay, plus Camp Cove in Port Jackson. A nested sampling design used five replicate collections for each species at two sites within each location. Whole plants were collected in plastic bags from low-tide transects, transported on ice, rinsed with deionized water, frozen, freeze-dried, and ground to powder. Total arsenic was measured after microwave nitric-acid digestion of 0.07 g freeze-dried sample and ICP-MS detection. Arsenic compounds were extracted from 0.0700-0.1000 g sample with 10 mL methanol/water mixtures, microwave-extracted for 5 min at 60 °C, centrifuged at 4000 rpm for 20 min, and characterized by HPLC-ICP-MS using a Hamilton PRP X-100 anion-exchange column and LC-MS/MS confirmation of arsenoriboside standards from Ascophyllum nodosum.

Implications

This paper contributes raw macroalgae arsenic occurrence and arsenic-speciation context from Australia. The source is not a retail or edible-product survey, but it shows that Sydney-area macroalgae can contain high total arsenic and that several species carry substantial As(V), As(III)/MA, or DMA fractions. Downstream routing should preserve the raw coastal-macroalgae context and the distinction between total As, inorganic arsenic species, DMA, and arsenoribosides.

Wiki pages this source may touch

• seaweed-kelp-foods
• seaweed
• arsenic-total
• arsenic-inorganic

Verification notes

• Identity checks before writing found no existing source page for DOI 10.1071/MF01230, raw handle MFK_tukai2002, title text, or cite key tukai2002-sydney-macroalgae-arsenic-speciation.
• Text was extracted to /tmp/hmi-seaweed-062.txt with pdftotext -layout; title/authorship, methods, Figure 2 summary text, Tables 1-3, discussion, conclusions, and references were readable.
• All Key numbers were checked against /tmp/hmi-seaweed-062.txt, especially the abstract class-level total-As ranges, Table 3 species rows, extraction percentages, and CRM recovery values.
• Units and bases are preserved as µg g-1, %, mL, g, min, °C, and rpm; no unit conversion was performed. The paper reports dry freeze-dried macroalgal powder for the analytical work.
• Speciation check: total arsenic, As(III)/MA, As(V), DMA, and arsenoribosides are kept distinct. The combined As(III)/MA Table 3 column is not separated into arsenite and methylarsenate because the source says the species overlapped.
• Tables 1 and 2 are Tukey HSD ranking tables rather than concentration tables; they were read but not reproduced as occurrence values.
• Brand firewall: no consumer brands are named. Ascophyllum nodosum material used as an arsenoriboside standard is method context only.
• Missing-slug check: no missing product or ingredient slug blockers. Exact macroalgal species remain in Key numbers while frontmatter uses broad seaweed/kelp food routing.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.